Lead in the environment is know to influence human exposure and to produce adverse health impact. Exposure to relatively high levels of lead has been evaluated in occupational setting, where exposed individuals have had chronic exposure, and in community settings, where inadvertent lead exposure to children has resulted in acute lead poisoning. However, the relationship relatively low environmental exposures to lead in a community setting are not well characterized. We propose to investigate the relationship between environmental lead concentrations by using standard exposure assessment protocols and biological markers of exposure. These biological markers are two; the standard blood lead measurement, and the newer, K-XRF technique for measuring bone lead in vivo. Several longitudinal sub-studies are planned. The major focus of this investigation is the repeated simultaneous measurement of environmental lead concentrations, blood lead concentrations, and bone lead concentrations in adolescents. The target group consists of high school students who are unlikely to have received significant occupational exposure to lead. The study will start with a baseline evaluation of the cohort, including questionnaire administration, environmental sampling in the around their homes, a blood lead measurement, and a bone lead measurement. This procedure will be repeated at one year intervals. Data will be analyzed to evaluate the relationship between current environmental lead level and blood lead, environmental level and bone lead concentrations, and the longitudinal relationship between these environmental and biological lead measures. Also, we propose to examine the ability of the bone lead technique to identify those adolescents who, in early childhood, were diagnosed as lead poisoned. Through this study and the following of adolescents for a period of several years, we hope to gain new insights regarding the kinetics of lead uptake by bone during this important growth period. Finally, we will examine the relationship between the ALA-D gene polymorphism on measured blood lead and bone lead concentrations, affording new insight on the impact of this mutation on the effects associated with a given lead exposure.